"""
流程控制
"""


def if_demo():
    x = int(input("please enter an integer: "))
    if x < 0:
        x = 0
        print("Negative changed to zero")
    elif x == 0:
        print("zero")
    elif x == 1:
        print("Single")
    else:
        print("more")

def while_demo():
    i = 0
    while i<10:
        print(i, end=',')
        i = i+1


def pass_demo():
    while True:
        pass


if __name__ == "__main__":
    pass_demo()
